Effect of temperature and aluminium on calcium (alumino)silicate hydrate chemistry under equilibrium conditions

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Myers, R.J., Provis, J.L., L'Hôpital, E. et al. (1 more author) (2014) Effect of temperature and aluminium on calcium (alumino)silicate hydrate chemistry under equilibrium

conditions. Cement and Concrete Research, 68. 83 - 93. ISSN 0008-8846 https://doi.org/10.1016/j.cemconres.2014.10.015

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Supporting information for:

Effect of temperature and aluminium on calcium

(alumino)silicate hydrate chemistry under equilibrium

conditions

Rupert J. Myers 1,2,a, Emilie L’Hôpital 2,b, John L. Provis 1,c, Barbara Lothenbach 2*

1

Department of Materials Science and Engineering, University of Sheffield, S1 3JD, Sheffield,

United Kingdom

2

Laboratory for Concrete and Construction Chemistry, EMPA, Dübendorf, 8600, Switzerland

* Corresponding author. Email [email protected]

a

Appendix S1. Details of the deconvolution method for the

Si MAS NMR

spectra

The 29Si MAS NMR spectra were deconvoluted using the structural constraints described here,

for C-(A-)S-H nanostructures with nearest-neighbour Al-O-Al avoidance [1]. A ratio of Q2p/Q2b

= 2 was specified for the non-cross-linked C-(A-)S-H products, which is required for consistency

with ‘dreierketten-type’ (3n-1) chain structures [2]. Additional constraints were specified for the

cross-linked C-(A-)S-H products [3], which are:

i) Q2(1Al) ≥ 2Q3(1Al);

ii) Q2 + Q2(1Al) ≥ 2(Q3 + 2Q3(1Al));

iii) Q2p* ≥ 0;

iv) Q2(1Al)* ≥ 0; and

v) Q2p*/Q2b = 2

Appendix S2. Additional details of the differential mass loss peak assignments

Additional XRD data were measured to support the differential mass loss peak assignments

described in the main body of the article. These data were obtained by heating C-(A-)S-H

samples (synthesised under the procedure described in section 2) in a Carbolite HTF 1700

furnace at a rate of 300°C/hour to upper and lower temperatures with respect to the differential

mass loss peaks analysed here (Table S1). The samples were held at the specified temperatures

for 1 hour, then cooled at a rate of ~30°C/minute to room temperature under laboratory

atmosphere, and subsequently stored in a desiccator (for up to 6 hours in the presence of SiO2

gel) until analysis.

Table S1. Lower and upper temperatures to which C-(A-)S-H samples were heated for analysis of differential mass loss peaks (Figure 3 and shown here). Ca/Si* = bulk Ca/Si. Al/Si* = bulk

Al/Si.

Ca/Si* Al/Si* Equilibration

temperature (°C)

Differential mass loss peak temperature (°C)

Lower temperature (°C)

Upper temperature (°C)

1 0.1 80 ~500 320 600

1 0.05 50 ~380 250 520

1 0 50 ~810 550-650 950

1 0.1 50 ~810 550-650 950

Figure S1 shows that heating the C-A-S-H samples equilibrated at 80°C with bulk Al/Si = 0.1 to

600°C, and heating the 50°C C-A-S-H samples with bulk Al/Si = 0.05 to 520°C, results in the

decomposition of C-A-S-H only. Heating these samples to 250°C (Figure S1B) or 320°C (Figure

S1A) transforms C-A-S-H to a phase with similar long-range order to 9 Å tobermorite

(represented by C3 in Figure S1, Ca5Si6O16(OH)2, PDF# 04-012-1761) [4]. The C-A-S-H phase

600°C (Figure S1A), which can be identified by the shift of the major 9 Å tobermorite reflections

(~29.5° 2 ) to higher angles.

Figure S1. Cu K diffractograms of C-A-S-H samples with A) bulk Al/Si = 0.1 and equilibrated at 80°C, and B) bulk Al/Si = 0.05 and equilibrated at 50°C, heated to the temperatures shown in

the plots.

Figure S2 shows Cu K diffractograms for C-(A-)S-H samples equilibrated at 50°C and heated

to 550-650°C and 950°C (bulk Al/Si = 0 and 0.1). Decomposition of C-(A-)S-H occurs up to

550-650°C, which is shown by the loss of the d(002) basal spacing peaks and shifting of the major

reflections at ~29° 2 to higher angles. Formation of a small amount of mayenite (C12A7, PDF#

S2B). Wollastonite (CaSiO3, PDF# 01-076-0925) is formed and decomposition of C-(A-)S-H

occurs during heating between 550-650°C and 950°C; complete decomposition of C-(A-)S-H is

attained after heating at 950°C for 1 hour. Mayenite is also formed in the C-A-S-H sample

during heating at 950°C (Figure S2B).

Figure S2. Cu K diffractograms of C-(A-)S-H samples equilibrated at 50°C with A) bulk Al/Si = 0 and B) bulk Al/Si = 0.05, heated to the elevated temperatures shown in the plots.

These results confirm the assignment of the differential mass loss peaks at ~380°C and ~500°C

peaks at ~810°C (Figure 3) to the decomposition of C-(A-)S-H to wollastonite. These data also

show that the thermal behaviour of the C-(A-)S-H products synthesised here is relatively similar

to that of 14Å tobermorite [5], which highlights the high level of structural and chemical

Appendix S3. Tabulated data relevant to the thermodynamic modelling

calculations, including aqueous phase compositions

Aqueous phase compositions and pH results for the C-S-H and C-A-S-H systems are shown in

Table S2, and log10(Kso) values for the C-(A-)S-H products calculated here (using the chemical

compositions determined by mass balance and reported in Table 3) are shown in Table S3.

Table S2. Aqueous phase compositions and pH results for the C-S-H and C-A-S-H systems. Al/Si* = bulk Al/Si.

Al/Si* = 0

Temperature (°C) [Si] (mM) [Ca] (mM) [Al] (mM) [OH-] (mM) pH †

7 0.025 2.0 0 2.6 11.4

20 0.083 3.2 0 3.9 11.7

50 0.091 2.8 0 5.9 11.7

80 0.11 1.7 0 4.4 11.6

Al/Si* = 0.05

Temperature (°C) [Si] (mM) [Ca] (mM) [Al] (mM) [OH-] (mM) pH †

7 0.046 2.0 0.020 2.9 11.5

20 0.15 2.1 0.020 5.2 11.8

50 0.10 2.4 0.003 5.3 11.6

80 0.073 1.9 b.d.l. ‡ 4.2 11.6

Al/Si* = 0.1

Temperature (°C) [Si] (mM) [Ca] (mM) [Al] (mM) [OH-] (mM) pH †

7 0.053 1.7 0.036 2.5 11.4

20 0.11 2.9 0.031 4.2 11.7

50 0.17 1.5 0.028 3.5 11.5

80 0.074 1.7 0.005 4.2 11.6

Al/Si* = 0.15

Temperature (°C) [Si] (mM) [Ca] (mM) [Al] (mM) [OH-] (mM) pH †

7 0.069 1.3 0.043 1.9 11.3

20 0.34 1.3 0.023 3.0 11.5

50 0.32 1.2 0.043 2.1 11.3

80 0.094 1.1 0.039 3.0 11.4

† pH measured at 23°C

Table S3. Solubility products for the C-(A-)S-H products with chemical compositions given in Table 3, which refer to the reaction given by eq.(6) and Ca2+(aq), SiO32-(aq), AlO2-(aq), OH-(aq)

and H2O (l). Al/Si* = bulk Al/Si.

Al/Si* = 0

Temperature (°C) log10(Kso)

7 -9.98

20 -8.91

50 -8.66

80 -8.80

Al/Si* = 0.05

Temperature (°C) log10(Kso)

7 -9.65

20 -8.83

50 -8.82

80 -9.08 †

Al/Si* = 0.1

Temperature (°C) log10(Kso)

7 -9.69

20 -8.68

50 -8.64

80 -9.21

Al/Si* = 0.15

Temperature (°C) log10(Kso)

7 -9.47

20 -8.52

50 -8.73

80 -9.35

Appendix S4. Detailed

Si MAS NMR spectral deconvolution results

The deconvoluted spectra for the C-S-H systems and the C-A-S-H samples with bulk molar

ratios of Al/Si = 0.1 are shown in Figures S3 and S4 respectively. The results are tabulated in

Table S4. Deconvolution results for the 29Si MAS NMR spectra. The estimated error in absolute site percentages is ±0.03. Al/Si* = bulk Al/Si.

Al/Si* Temperature (°C)

Q1 -79.4 ±0.3 ppm

Q2(1Al) -81.9 ±0.2 ppm

Q2b -83.5 ±0.3 ppm

Q2p -85.3 ±0.3 ppm

Q3(1Al) -91.9 ppm

Q3 -96.6 ppm

Al/Si MCL

0 7 0.31 0 0.23 0.46 0 0 0 6.5

0 20 0.36 0 0.21 0.43 0 0 0 5.6

0 50 0.32 0 0.23 0.46 0 0 0 6.4

0 80 0.23 0 0.26 0.51 0 0 0 8.8

0.1 7 0.19 0.16 0.22 0.43 0 0 0.081 11.4

0.1 20 0.21 0.17 0.21 0.42 0 0 0.084 10.4

0.1 50 0.20 0.16 0.21 0.43 0 0 0.082 11.0

References in this supporting information file:

1. W. Loewenstein, The distribution of aluminum in the tetrahedra of silicates and

aluminates, Am. Mineral., 39 (1954) 92-96.

2. I.G. Richardson, Tobermorite/jennite- and tobermorite/calcium hydroxide-based models

for the structure of C-S-H: applicability to hardened pastes of tricalcium silicate,

-dicalcium silicate, Portland cement, and blends of Portland cement with blast-furnace

slag, metakaolin, or silica fume, Cem. Concr. Res., 34 (9) (2004) 1733-1777.

3. R.J. Myers, S.A. Bernal, R. San Nicolas, J.L. Provis, Generalized structural description of

calcium-sodium aluminosilicate hydrate gels: the cross-linked substituted tobermorite

model, Langmuir, 29 (2013) 5294-5306.

4. S. Merlino, E. Bonaccorsi, T. Armbruster, The real structures of clinotobermorite and

tobermorite 9Å: OD character, polytypes, and structural relationships, Eur. J. Mineral., 12

(2) (2000) 411-429.

5. C. Biagioni, E. Bonaccorsi, S. Merlino, D. Bersani, New data on the thermal behavior of